Solve for $n$ : $18 = -19 + n$
Add $19$ to both sides: $ \begin{eqnarray} \\ \hphantom{18 {+ 19}} &\hphantom{=}& \hphantom{n} \\ 18 &=& -19 + n \\ \\ {+19} && {+19} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 18 {+ 19} &=& n \\ \end{eqnarray} $ Simplify. $ n = 37$